M.Sc. STUDY
Laboratory Study of Time Variance Equation For Degradation Downstream Hydraulic Structures
College of Engineering, the University of Mosul
M.Sc. Awarded in 2008
Have you ever thought about the vital role rivers play in our lives? Since the beginning of time, these majestic waterways have been a source of life and prosperity, but also a force of nature to be respected. Throughout history, humans have built structures to control and manage rivers, like dams and weirs. But these structures can be vulnerable to a process called degradation, where the riverbed slowly erodes downstream.
In my Master's thesis, I investigated this phenomenon of degradation. Previous studies often ignored the presence of sediment, the tiny particles that rivers carry. My research aimed to understand how degradation works in a more realistic setting, with sediment flowing in the water.
The Experiment
Imagine a miniature river channel built inside a lab. That's what I used to simulate degradation! I filled the channel with washed river sand and then ran water through it. In some experiments, the water was clear, and in others, I added different amounts of sediment. By carefully monitoring the channel over time, I observed how the riverbed changed.
The Findings
The experiments revealed some fascinating insights. Degradation turned out to be a complex process, influenced by many factors. Just like a detective searching for clues, I wanted to find a way to predict how deep the degradation would become over time.
One of the key findings was the impact of dams and barriers. These structures disrupt the natural flow of the river, causing sediment to build up upstream. Downstream, the water loses its erosive power because it's moving slower. The experiments showed that degradation was most severe within the first meter or so downstream from the structure, and then it gradually lessened further downstream.
The amount of sediment in the water also played a role. The more sediment there was, the less the riverbed degraded. This is because the sediment particles would settle down and partially protect the riverbed from erosion.
Interestingly, the size of the sand particles in the riverbed also changed during degradation. In clear water, the particles tended to get bigger. But when sediment was present in the water, the particle size could either increase or decrease.
Finally, under stable flow conditions, a fascinating phenomenon occurred. A rough layer of sediment formed on the riverbed, like a natural armor plate. This layer, which I called "Layer Armor," seemed to resist further erosion.
Recommendations
My research opened doors for further exploration. I believe future studies should investigate how different types of sediment and channel slopes affect degradation. Additionally, it would be valuable to see if the findings from my lab experiments can be applied to real rivers in the field.
Conclusion
Understanding degradation is essential for ensuring the safety and longevity of hydraulic structures. By studying this phenomenon in detail, we can build more sustainable and resilient river management systems.
QUALIFICATION DETAILS:
M.Sc. Thesis Details:
TITLE: Laboratory Study of Time Variance Equation For Degradation Downstream Hydraulic Structures
AUTHOR: Dilshad Abduljabbar Haleem
ISSN:
AWARDING BODY: The College of Engineering, The University of Mosul
CURRENT INSTITUTION: The University of Duhok
DATE AWARDED: 2008
Full Text Link: [PLEASE CLICK TO VIEW THE FULL TEXT OF MY M.Sc.]
SUPERVISOR: Assistant Professor Dr. Khalid S. Al-Shaikh - Ali
SPONSOR: The University of Duhok and The University of Mosul
QUALIFICATION NAME: Degree of Master of Science in Water Resources Engineering
QUALIFICATION LEVEL: M.Sc.
LANGUAGE OF THE THESIS: Arabic
REPOSITORY LINK:
Citation to this work:
Haleem, DA, (2008), Laboratory Study of Time Variance Equation For Degradation Downstream Hydraulic Structures, M.Sc. Thesis, The University of Mosul,
Abstract:
This study investigated degradation, the erosion of the riverbed downstream of hydraulic structures like dams and weirs. Prior research often neglected the presence of sediment. Here, laboratory experiments simulated degradation in a mobile sediment channel with and without sediment flow. The study aimed to understand how the gradient of surface layer materials changes over time and distance, and to develop an equation for calculating degradation depth and width. Experiments used a channel filled with washed river sand. Clear water flowed in the first set of experiments (42), while the second set (54) introduced varying sediment concentrations. Findings revealed degradation as a complex phenomenon influenced by multiple factors. Constructing dams disrupts natural flow dynamics, leading to upstream sedimentation and reduced downstream erosion. Degradation diminished over time and distance, particularly within the first meter downstream. Higher sediment concentrations resulted in shallower degradation. The size of surface layer material exhibited significant changes by the end of the degradation process. Under stable flow conditions, a rough monolayer, termed "Layer Armor," formed, potentially resisting further erosion. The study recommends future research using diverse sediment models, applying findings to real rivers, and investigating the influence of sediment type and channel slope on degradation.
Keywords:
Degradation, Hydraulic Structures, Sediment Transport, Riverbed Scour, Layer Armor
Reference List:
Newton, C., T. (1951). 'An experimental investigation bed degradation in an open channel', Trans., of Boston Society of Civil Engineers, From Gessler. (1971).
Tinney, E. R. (1962). 'The progress of channel degradation', Journal Of Geophysical Research, Vol. 67, No. 4, pp. 1475 – 1480.
Garde, R. J., and Hassan, S., M. (1967). 'An Experimental Investigation of Degradation in Alluvial Channels', Proceedings 12th Congress of International Association for Hydraulic Research, Fort Collins, Colorado, Vol.3, pp. 38-45. From (Khalil 1991).
Gessler, J. (1971). 'Aggradation and Degradation', River Mechanics, Edited and Published by H.W. Shen, Vol. 1, Chapter 8, For Collins, Colorado, USA.
Little W.C., Mayer P.G. (1972). 'The role of Sediment Gradation on Channel Armouring', Pub. N. ERC-0672, Georgia institute of technology, Atlanta, Ga., 1972. From (Termini D 1998).
Hammad, Y., H. (1972). 'River Bed Degradation After Closure at Dams', Journal of Hydraulic Divisions, ASCE, Vol. 98, pp.591-606, April. From (Lu And Shen 1986).
Garde, R.J., and AL Shaikh, A. (1977). "Armoring process in degrading streams" Journal of Hydraulic Division ASCE, VOL.103, NO.9, PP: 1091_1095.
Garde, R. J., and Ranga Raju, K. G. (1977). "Mechanics of sediment transportation and alluvial stream problems" Wiley Eastern, New Delhi, ch. 12, pp. 296-297.
Phillips, B. C., and Sutherland, A. J. (1985). "Diffusion models applied to channel degradation application des models de diffusion erosion deslits fluviaux" Journal of Hydraulic Research VOL.25, NO.3, PP:179-191.
Lu, Y.J., and Shen, M. (1986). "Analysis and comparisons of degradation models" Journal of Hydraulic Engineering ASCE, VOL.112, NO.4, PP: 281–299.
Lee, H.Y., and Odgraad, A.J. (1986). "Simulation of bed armoring in alluvial channels" Journal of Hydraulic Engineering ASCE, VOL.112, NO.9, PP: 794_801.
Karim, M.F., and Holly, J. (1986). "Armoring and sorting simulation in alluvial rivers" Journal of Hydraulic Engineering ASCE, VOL.112, NO.8, PP: 705_715.
Holly, J., and Karim, M.F. (1986). "Simulation of Missouri River bed degradation" Journal of Hydraulic Engineering ASCE, VOL.112, NO.6, PP: 497_517.
Borah, D.K. (1989). 'Scour Depth Prediction under Armoring Conditions', Journal of Hydraulic Engineering, ASCE, Vol.115, No.10, pp. 1241-1245.
Khalil, I. O. (1991). 'Effect of Bed Material Size on Degradation Downstream Sluice Gate' M.Sc. Thesis, College of Engineering, University of Mosul.
Simons, B. D., and Senturk, F. (1992). "Sediment transport technology" Water Resources Publication, Fort Collins, Colorado, U. S. A.
Chin, C.O., Melville, B.W., and Raudkivi, A.J. (1994). "Streambed armoring" Journal of Hydraulic Engineering ASCE, VOL.120, NO.8, PP: 889_918.
Termini, D., and Bonvissuto, G. (1998). 'Numerical Simulation of Bed Degradation and Bed Armouring', From Internet. Dipartimento di Ingegneria idraulic ed Applicazioni Ambientali Universita di Palermo, E-mail: dia@idra.ing.unipa.it.
Gareth, P., Hoey, T., Chris, F., and Mcewan, J. K. (2000). 'Selective bed load transport during the degradation of a well sorted graded sediment-bed', Journal of Hydraulic Research, Vol. 39, No. 3, pp.269-277.
Albert, M., and Baosheng, WU. (2000). 'Transport of Sediment in Large Sand-bed Rivers' journal of Hydraulic Research, Vol. 39, No.2, pp. 135-146.
Chiew, Y. M. (2004). "Local scour and riprap stability at bridge piers in a degrading channel" Journal of Hydraulic Engineering ASCE, VOL.130, NO.3, PP: 218_226.